The Triangulum Galaxy is a spiral galaxy approximately 3 million light years (ly) from Earth in the constellation Triangulum. The Triangulum Galaxy is the third-largest member of the Local Group of galaxies, which includes the Milky Way Galaxy, the Andromeda Galaxy and about 50 other smaller galaxies. It is one of the most distant permanent objects that can be viewed with the naked eye.
- Brunthaler, Andreas et al (2005). "The geometric distance and proper motion of the Triangulum Galaxy (M33)". Science 307 (5714): 1440–1443. doi:10.1126/science.1108342. PMID 15746420.
- Karachentsev I. D. et al (2004). "A catalog of neighboring galaxies". Astronomical Journal 127 (4): 2031–2068. doi:10.1086/382905.